1. Field of the Invention
The present invention relates to a method of drying a semiconductor wafer, and more specifically, to a method of drying the semiconductor wafer so as to rinse residual etching reactants/product from the surface of the semiconductor wafer.
2. Description of the Prior Art
In semiconductor processing, lithography and etching are two commonly used processes. During lithography, light is projected from above through a photo mask onto a photoresist layer coated on a semiconductor wafer. The photoresist layer on the wafer is then exposed and developed thus creating a pattern corresponding to that of the photo mask. During etching, materials such as silicon or SiO2 in areas on the semiconductor wafer not covered by the photoresist layer are etched followed by removal of remaining photoresist. Therefore, developing effective and accurate methods to transfer the pattern of the photo mask onto the semiconductor wafer through use of lithography and etching continues to be a top priority.
Please refer to FIG. 1 of a schematic view of rinsing residual etching reactants/product on the surface of a semiconductor wafer 10 according to the prior art. As shown in FIG. 1, a semiconductor wafer 10 is positioned on an etching machine 12 comprising a cleaning solution sprayer 14 above a center of the semiconductor wafer 10.
The semiconductor wafer 10 is spun at the beginning of the rinsing method according to the prior art. Simultaneously, a cleaning solution 16, primarily composed of deionized water (DI water), is sprayed on the center of the surface of the semiconductor wafer 10 via the cleaning solution sprayer 14. Therefore, the residual etching reactants/product on the surface of the semiconductor wafer 10 is rinsed. Finally, the semiconductor wafer 10 is spun dry with a nitrogen purge on the surface of the semiconductor wafer 10 (not shown), at the end of the rinsing method according to the prior art.
However, the method of rinsing residual etching reactants/product on the surface of the semiconductor wafer 10 according to the prior art is to spray the cleaning solution 16 on the center of the semiconductor wafer 10 merely via the cleaning solution sprayer 14. By performing a spinning-dry process with a nitrogen purge on the center of the semiconductor wafer 10, the residual etching reactants/product on the surface of the semiconductor wafer 10 is rinsed by portions of the cleaning solution 16 sprayed on the center of the semiconductor wafer 10. Both portions of the cleaning solution 16 and most of the residual etching reactants/product are then removed from the semiconductor wafer 10 by centrifugal force caused by the spinning-dry process. Therefore, light amount of the etching solution normally resides and over-etches the edge of the semiconductor 10 so as to cause defects that affect the quality of the semiconductor wafer 10. This then can lead to reduced yield rates in subsequent processes and reduce the quality of the product.
It is therefore a primary objective of the present invention to provide a method of cleaning the surface of a semiconductor wafer so as to rinse residual etching reactants/product from the surface of the semiconductor wafer.
In the preferred embodiment of the present invention, a semiconductor wafer is positioned on an etching machine comprising a cleaning solution sprayer. The cleaning solution sprayer comprises at least a first nozzle positioned above a center of the wafer center, and a second nozzle positioned above an edge of the wafer. At the beginning of the method provided in the present invention, the semiconductor wafer is spun. Simultaneously a cleaning solution is sprayed on the center and the edge of the wafer via the first nozzle and the second nozzle, respectively, to evenly rinse the residual etching reactants/product from the surface of the semiconductor wafer. Finally, a spin-drying process is performed on the semiconductor wafer with a nitrogen purge on the wafer surface at the end of the method. The preferred period of the nitrogen purge ranges from 30 to 50 seconds.
It is an advantage of the present invention against the prior art that the cleaning solution sprayer comprises a first nozzle and a second nozzle, so that the cleaning solution is sprayed on the center and the edge of the semiconductor wafer via the first nozzle and the second nozzle, respectively. This means that the residual etching reactants/product on the surface of the semiconductor wafer is evenly and thoroughly rinsed so that an over-etch on the edge of the semiconductor wafer caused by residual etching reactants/product is prevented. As a result, the quality of the semiconductor wafer and the yield rates of subsequent processes are significantly improved.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the multiple figures and drawings.